Exposing more than 2 instances of the same thing generates duplicate URIs

[derwehr]

When exposing multiple Things with the same title via the HTTP bindings, expose() invokes generateUniqueName here to append _2, and then does not check whether title_2 already exists.

Changing the if in http-server.ts#L272 to a while fixed this for me.

I.e:

while (this.things.has(urlPath)) {
    urlPath = Helpers.generateUniqueName(urlPath);
}

[danielpeintner]

Note: Generally I think Helpers.generateUniqueName(...) is not a good helpers' method (it does not know about the existing names etc) and should be deprecated as is. I believe the requirement to generate unique names/urls can be handled very easily locally in each binding and is much more flexible.

#1375 shows that...